// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_MESSAGE_CENTER_NOTIFICATION_BLOCKER_H_
#define UI_MESSAGE_CENTER_NOTIFICATION_BLOCKER_H_

#include "base/observer_list.h"
#include "ui/message_center/message_center_export.h"
#include "ui/message_center/notification.h"

namespace message_center {
class MessageCenter;

// NotificationBlocker manages the availability of notifications based on the
// current system status. Each NotificationBlocker implementation covers a
// single state such as screen lock or fullscreen.
class MESSAGE_CENTER_EXPORT NotificationBlocker {
public:
    class Observer {
    public:
        virtual void OnBlockingStateChanged(NotificationBlocker* blocker) = 0;
    };

    explicit NotificationBlocker(MessageCenter* message_center);
    virtual ~NotificationBlocker();

    void AddObserver(Observer* observer);
    void RemoveObserver(Observer* observer);

    // Checks the current state and updates the availability.
    virtual void CheckState() { }

    // Returns true when notifications from |notifier_id| should appear in the
    // message center. Default returns true always.
    virtual bool ShouldShowNotification(const NotifierId& notifier_id) const;

    // Returns true when notifications from |notifier_id| should be shown as
    // popups on screen.  If it's false, those notifications should be queued.
    // When a blocker starts returning false for a notification which is already
    // shown as a popup, the notification should be closed as a popup immediately.
    virtual bool ShouldShowNotificationAsPopup(
        const NotifierId& notifier_id) const = 0;

protected:
    MessageCenter* message_center() { return message_center_; }
    void NotifyBlockingStateChanged();

private:
    base::ObserverList<Observer> observers_;
    MessageCenter* message_center_; // weak
};

typedef std::vector<NotificationBlocker*> NotificationBlockers;

} // namespace message_center

#endif // UI_MESSAGE_CENTER_NOTIFICATION_BLOCKER_H_
